1. Field of the Invention
This invention relates to a device for measuring a physicality of a food such as an agricultural product and a method for measuring the food physicality. Particularly, this invention relates to a device and a method for measuring the texture of the food using an acoustic signal or an oscillating spectrum which is generated by piercing a probe with a given shape into the food.
2. Description of the Prior Art
A person judges his or her likes and dislikes for foods by various factors such as taste, flavor and color. Among the factors, the textures for foods are very important in the judgment of likes and dislikes. For example, the crispy texture of fresh lettuce and celery and the mature texture of pear affect on the likes and dislikes of the person. Such a texture of a food is originated from the kinetic property (elasticity or viscosity) of the food. Therefore, the food texture can be quantified by measuring the kinetic property such as elasticity or viscosity of the food.
Conventionally, various methods for measuring the kinetic property of the food have been proposed. For example, the method for quantifying the texture of noodles or pastas is disclosed in Japanese Patent Application Laid-open No. 11-190688. Until that time, the texture of the noodles or the pastas is dubiously defined. Moreover, the method for measuring textures of foods which particularly, babies like is disclosed in Japanese Patent Application Laid-open No. 2000-283975.
In a conventional technique as mentioned above, a plunger is pierced into a food and then, lifted to measure the texture of the food by utilizing the kinetic property (stress or adhesive force) which is loaded to the plunger. In order to perform a precise measurement, the shape of the plunger is improved and changed on the sort of food. With the conventional technique, however, it is difficult to measure textures of various foods precisely.
For example, it is difficult to define the mature degree of pear, the texture of which is drastically changed in ripe to turn into a so-called buttery state. Therefore, the texture of pear is defined in sense by a person of experience and thus, can not be quantified, which poses great problems on distributive trade.
FIG. 5 is a graph showing the flesh hardness of a pear with time which is measured by utilizing a rheometer (CONPAC-100 made by San Science Industries, Co. Ltd.). In the measurement, a conical shaped plunger is employed, and pierced into the pear processed in a given size at a given constant rate. The flesh hardness is estimated from the stress when the plunger is pierced by a predetermined distance.
FIG. 6 is a graph showing the mature degree in sense of a pear with time. The reference numeral “5” designates “green degree”, and the reference numeral “4” designates “semi-green degree”, and the reference numeral “3” designates “semi-mature degree”. The reference numeral “2” designates “mature degree”, and the reference numeral “1” designates “over-mature degree”. The green degree means the texture of flesh pear, and the mature degree means the texture of mature pear, so called buttery state.
As is apparent from FIGS. 5 and 6, the flesh hardness of the pear is decreased to 2.5 between the seventh day and the ninth day of the measurement. In this case, the kinetic property of the pear is changed drastically, and then, the texture of the pear turns into a buttery state. Thereafter, the mature degree of the pear proceeded, and turns into an over-mature degree at the fifteenth day of the measurement. However, the flesh hardness is not almost changed after the tenth day of the measurement from FIG. 5. Therefore, in the conventional technique, the flesh hardness is not correlated with the mature degree in sense.
The above result teaches that in the conventional technique, the food physicality can be detected on the kinetic property, but the subtle mature degree of the food can not be detected because the complicated and subtle physicality of food such as pear can not be detected on the kinetic properties of food such as hardness or adhesive force.